The present invention relates to making insulating glass assemblies using a low-temperature press process.
Insulating glass assemblies such as insulating glass (IG) units and insulating sash assemblies often include a pair of glass panes maintained in a fixed spaced relation to each other by a spacing structure (spacer) and sealing structure that extends around the periphery of the inner facing surfaces of the glass sheets to define a sealed and insulating space between the glass panes. In the case of insulating sash assemblies, the spacer is an integral part of the sash frame and the glass panes are attached to the spacer by a sealant or adhesive composition. The sealant or adhesive composition is also used to seal the edges of the insulating glass assembly so as to establish a barrier that prevents moisture from penetrating into the interior of the assembly and potentially to prevent thermally insulating gases, like argon, from leaving the airspace.
Many construction materials are used in manufacturing insulating glass assemblies, including wood, metals (e.g., aluminum and steel), polymers such as polyvinyl chloride and composites (e.g., wood fiber reinforced polymer composites and fiberglass reinforced polymer composites). Insulating glass assemblies that include a thermoplastic spacer (e.g., polyvinyl chloride) can experience distortion and deformation when exposed to elevated temperatures leading to residual stresses in the bond line, which can then lead to a loss of bond integrity, bond durability, an increase in the potential for stress cracking and moisture intrusion into the sealed chamber of the assembly. Build up in residual stresses in the bond line is exacerbated by the mismatch in the coefficients of thermal expansion due to the dissimilar substrates (e.g., glass panes and a thermoplastic spacer).
Conventional insulating glass windows are currently manufactured in a two step process in which a stand-alone subassembly consisting of two pieces of glass and a spacer, which is referred to as an “insulating glass unit,” is inserted into a sash frame to produce an insulating sash subassembly. The insulating sash is installed into a frame to make a window. Insulating glass units are typically manufactured according to processes known as “linear extrusion,” SWIGGLE sealing, and hand gunning.
Hand gunning involves applying a sealant to a channel formed by the two panes of glass and the spacer. The sealant is either a two-component sealant, which is applied at room temperature or a single-component sealant, which is applied at relatively high temperatures (e.g., temperatures of at least 200° F.). Two-component sealants require metering, mixing and monitoring of the ratio of the two components. Two-component sealants also require time to cure to a sufficient degree to be suitable for handling and the equipment used to dispense the sealant is purged periodically to prevent blockage. Hot applied single-component sealants require a high application temperature, which can create safety issues. Hand gunning is often used to apply sealants to aluminum spacers, which have poor thermal performance. The nature of hand gunning results in a relatively low throughput and consequent higher cost per unit. Automated or semi-automated application equipment is costly.
Residential insulating glass units are often manufactured using a lineal extrusion process, which is referred to by the trade designation INTERCEPT. A linear extrusion process is described, e.g., in U.S. Pat. No. 5,177,916 (Misera) and U.S. Pat. No. 6,223,414B1 (Hodek). Linear extrusion involves coating the bottom inside of a channel of a spacer, which is typically made from metal. A desiccant matrix is often positioned on the inside bottom of the channel. The desiccant matrix is used to dry the insulating glass unit airspace and potentially remove chemical volatiles that may cause chemical fog from the airspace of the unit. At least one sealant is applied to the outer three sides of the spacer and a pair of glass panes are placed on the sealant on opposite sides of the spacer. The insulating glass unit is then passed through an oven heated to an air temperature in excess of 200° F. and a press, which is positioned in the oven, to adhesively bond the glass to the spacer. The pressure exerted on the insulating glass unit is at least 5 psi. High temperature and pressure is necessary to generate a sufficient bond between the glass and the spacer. Rollers are employed to apply pressure and move the unit through the oven.
Another insulating glass unit manufacturing technology is referred to by the trade designation SWIGGLE and involves the use of a rope-like product that includes a sealant, desiccant, and a spacer. The rope is positioned between two panes of glass and passed through a roller oven/press to bond the panes of glass together at oven air temperatures in excess of 160° F. Roller oven/press processes require relatively large amounts of energy and additional equipment for complex manufacturing and handling hot insulating glass assemblies.
Once the insulating glass unit is prepared, the unit is then secured in a frame, which is referred to as “glazing.” Glazing is typically accomplished by one of two processes. In one process, an adhesive strip or glazing tape is attached to a structure on the profile (i.e., “glazing leg”) of a frame and the insulating glass unit is adhered to the exposed surface of the glazing tape. Glazing stops or beads are then placed over the insulating glass unit in order to provide static pressure against the unit, reduce the UV light exposure and improve visual look of the sash.
In another process, which is referred to as “back-bedding sealing,” a sash frame is placed horizontally on an X-Y back-bedding machine that is capable of laying down a continuous bead of sealant along the glazing leg. The insulating glass unit is then adhered to the bead of sealant and glazing stops are attached to the sash. The back bedding sealant forms a seal between the insulating glass unit and the sash frame.
A relatively new window construction has been developed and utilizes an integrated sash design whereby the insulating glass assembly is an integrated part of the sash, i.e., the frame and insulating glass unit are not separate components. A variety of integrated insulating glass assemblies are available and are described in, e.g., U.S. Pat. No. 5,653,073 (Palmer), U.S. Pat. No. 6,055,783 (Guhl et al.), U.S. Pat. No. 6,286,288 (France), and U.S. Pat. No. 6,401,428 (Glover et al.).
These numerous commercially available approaches provide some flexibility in both the final window design and in the materials selected to make the windows. However, most approaches utilize sealant compositions that require application at elevated temperatures and pressures to achieve the desired properties, which consume relatively high amounts of energy. Heat may also distort the spacer and frame. There remains a need for systems that utilize sealant compositions capable of bonding a glass pane to a spacer without high temperature and pressure.